Summary

Cloud processes, such as precipitation formation, are among the most challenging research frontiers aimed at improving weather and climate predictions, as they must cover a variety of time and space scales for different cloud types. This colloquium is intended to introduce students to this frontier by exposing them to examples of current state of the art models aimed at different scales of simulation, together with recent field research that is targeted at improving the representation of cloud processes in these models. This colloquium is intended for advanced graduate students or, in some cases post-docs, whose interests may include cloud and aerosol physics, radar meteorology, and numerical simulation. It will feature lectures from experts on: Airborne and ground based measurements (both in situ and remote), field campaign data collection and project/data management, characteristics of numerical models at various scales, and recent research results using models and observations. Students will examine data from recent field campaigns (see below), together with corresponding numerical model output, under the mentorship of experts in model development and observational research. Numerical model output from both small scale and global models (the System for Atmospheric Modeling for large eddy simulation, the Weather Research and Forecasting model, and the Community Earth System Model) will be provided for students to compare to observations. The purpose is to explore analysis of cloud observations, as well as evaluation of model cloud schemes with observations.

The Profiling of Winter Storms (PLOWS) field program is focused on obtaining a greater understanding of the mesoscale structure and dynamics of cyclonic weather systems and the improvement of 0-48 hr cool season quantitative precipitation forecasts. Variability in the location, type, and intensity of precipitation is often determined by precipitation banding and/or embedded convection, particularly in the northwest and warm frontal quadrant in cyclones where frontal structures and associated frontal circulations are modified by deformation flow.

The PECAN (Plains Elevated Convection at Night) campaign was envisioned as a multi-agency project (NSF, NOAA, NASA, DOE) designed to advance the understanding of continental, nocturnal, warm-season precipitation. PECAN was focused on nocturnal convection in conditions over the Southern Great Plains with a stable boundary layer (SBL), a nocturnal low-level jet (NLLJ) and the largest CAPE (Convectively Available Potential Energy) located above the SBL. Thunderstorms are most common after sunset across this region in summer and much of the resulting precipitation falls from mesoscale convective systems (MCSs). Nocturnal MCSs may produce heavy rainfall; their intensity is correlated with the NLLJ. To date, an accurate prediction and an in-depth understanding of elevated convection in this environment remains an elusive goal.

The Cloud Systems Evolution in the Trades (CSET) study was designed to describe and explain the evolution of the boundary layer aerosol, cloud, and thermodynamic structures along trajectories within the north-Pacific trade-winds using the NSF/NCAR Gulfstream V (HIAPER). This effort included characterization of the cloud, precipitation and aerosol fields in the stratocumulus and the fair-weather cumulus regimes within the subtropical easterlies over the northern Pacific.

Expected Outcome:

recent research projects together with mentors, to better understand the uses and limitations of both numerical simulations and field measurements.

This colloquium will be held at the National Center for Atmospheric Research in Boulder, CO, USA. In addition to receiving excellent scientiﬁc training, participants will have the opportunity to explore the National Center, will receive guidance on career planning and professional development, and- if time allows- will have access to additional seminars and activities at the Center.

Project descriptions:

During the colloquium, in addition to having lectures on a wide range of topics, you will have the chance to work in a small group with mentors on comparisons between model simulations and field campaign data.

The models include a climate scale model (CAM), a weather prediction model (WRF) and a Large Eddy Simulation (LES).

CAM will be paired with the Cloud Systems Evolution in the Trades (CSET) campaign, a study of boundary layer to cumulus transition clouds. The LES will also be paired with CSET. This will allow comparisons between the LES-scale simulations and the large-scale simulations of CAM, together with the field observations.

WRF will be paired with the Plains Elevated Convection at Night Campaign (PECAN) and the Profiling of Winter Storms (PLOWS) campaign. PECAN is a nighttime deep convection study, while PLOWS focused on winter extra-tropical cyclonic system.

you may wish to visit the web pages and field catalogs for these campaigns, where a wealth of information and data resides. These are located at: